In a tearful video, Ms Begum, 27, said there was no indication her younger sister had been thinking of leaving for Syria and said her disappearance had left "a big hole" in the family house.

She said Shamima had been "upset" after a friend from her school left for Syria and said the family was hoping the girls had "gone to go and bring her back".

Shamima was last seen on Tuesday morning when she was dropped off at a bus stop, claiming she had extra classes at school.

"There was no indication whatsoever. She was just herself. There was nothing different about her. There were no changes in her behaviour in anything. She was just our baby, she was just herself," Ms Begum said.

"We don't want her to do anything stupid - she is a sensible girl," she said, adding: "We just want her home, we want her safe."

Ms Begun said the three girls were "young" and "vulnerable" and if anybody had tried to persuade them to go to Syria it was a "cruel and evil" thing to do.

"They're preying on young innocent girls and it's not right," she added.

'Please think twice'

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Media captionAbase Hussen said his daughter had said goodbye to him in a normal way: "There was no sign to suspect her at all"

Mr Hussen said his daughter, Amira, had told him she was going to a wedding on Tuesday and sent a text between 10:00 and 11:00 GMT.

"She said, 'Dad the place is a little bit far. I pray my midday prayer and I get back.' She didn't come home," he said.

The family reported Amira as missing that night.

"We are depressed, and it's very stressful," he said while holding a teddy Amira had given her mother for Mother's Day.

"The message we have for Amira is to get back home. We miss you. We cannot stop crying. Please think twice. Don't go to Syria."

He said his daughter had never spoken about an interest in the militant group with him.

"She doesn't dare discuss something like this with us. She knows what the answer would be," he said.

In a further direct appeal to his daughter, he said: "Remember how we love you. Your sister and brother cannot stop crying."

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Media captionIn a statement, the sister of Kadiza Sultana - Halima Khanom - said ''we all miss you and love you''

Halima Khanom, the eldest sister of Kadiza, said her family was "hurting" and urged her to contact them.

In a direct appeal, she said: "Find the courage in your heart to contact us and let us know that you are safe and you are okay. That is all we ask of you."

Police say the girls boarded a Turkish Airlines flight, which departed from Gatwick Airport at 12:40 GMT for Istanbul.

Officers said the girls had previously been interviewed after another girl from their school - Bethnal Green Academy, in east London - went to Syria in December, but nothing had indicated they were at risk.

'Questions to answer'

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Family members of Amira Abase and Shamima Begum after making the appeals

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Renu, the eldest sister of missing British girl Shamima Begum, holds a picture of her sister

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A "No. 1 Mum" Chelsea FC teddy that Amira gave to her mother on Mother's Day